Internal combustion engine air-fuel ratio control system utilizing oxygen sensor

Abstract

An air-fuel ratio control system for an internal combustion engine utilizes an oxygen sensor to maintain a 14.5/1 air-fuel ratio at a first location in an intake manifold to an engine combustion chamber. A method and apparatus is disclosed for adding fuel and/or air to the air-fuel mixture at a second location, between the first location and the engine combustion chamber, so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.

What is claimed is: 
     
       1. A method for controlling the air-fuel ratio in an internal combustion engine having a combustion chamber arranged to operate at subatmospheric pressures, an intake manifold communicating with the combustion chamber for providing a flow of air to the combustion chamber, adjustable throttle means in the intake manifold for controlling the flow of air through the intake manifold, and fuel pumping means for introducing a first flow of fuel into the intake manifold and producing an air-fuel mixture, the method comprising the steps of: continuously sampling the air-fuel ratio of the mixture flowing adjacent a first loation in the intake manifold;   continuously adjusting the air-fuel ratio at the first location to the stoichometric value by adjusting the first flow of fuel into the intake manifold;   substantially continuously providing an additional flow of air at a second location in the intake manifold, spaced apart from the first location in the direction of the combustion chamber, and   introducing a second flow of fuel into the intake manifold adjacent the second location in an amount sufficient to reduce the air-fuel ratio of the mixture flowing into the combustion chamber below the stoichometric ratio when engine acceleration is desired.   
     
     
       2. The method of claim 1 wherein the stoichometric value of air-fuel mixture is essentially 14.5/1. 
     
     
       3. A method according to claim 1 wherein the step of continuously sampling comprises the steps of: continuously burning a portion of air-fuel mixture flowing adjacent the first location in a second combustion chamber which is spaced apart from the engine and the intake manifold, and   continuously detecting the amount of oxygen present in the second combustion chamber with an oxygen sensor having a continuous output signal which varies with the amount of oxygen detected.   
     
     
       4. A method according to claim 3 wherein the steps of continuously adjusting includes the steps of: amplifying and inverting the output signal from the oxygen sensor, and   transmitting the amplified and inverted signal to the fuel pumping means for varying the first flow of fuel into the intake manifold to thereby adjust the sampled air-fuel ratio to the stoichometric value.   
     
     
       5. An air-fuel ratio control system for an internal combustion engine having a combustion chamber arranged to operate at subatmospheric pressures, an intake manifold communicating with the combustion chamber for providing a flow of air to the combustion chamber, adjustable throttle means in the intake manifold for controlling the flow of air through the intake manifold, and a first fuel pumping means for introducing a first flow of fuel into the intake manifold and producing an air-fuel mixture, the control system comprising: first control means, said first control means including means for continuously sampling the air-fuel ratio of the mixture at a first location in the intake manifold and including means for continuously adjusting the first fuel pumping means to adjust the sampled air-fuel ratio to the stoichometric value for the mixture,   second air inlet means disposed at a second location in the intake manifold spaced apart from the first location in the direction of the combustion chamber, the second air inlet means being operative to provide a substantially continuous additional flow of air to the intake manifold, thereby normally increasing the air-fuel ratio of the mixture flowing into the combustion chamber above the stoichometric value, and   second control means, said second control means including a second fuel pumping means operative when engine acceleration is desired to introduce a second flow of fuel into the intake manifold at a third location spaced apart from the second location in the direction of the combustion chamber in an amount sufficient to reduce the air-fuel ratio of the mixture flowing into the combustion chamber below the stoichometric value.   
     
     
       6. The system claimed in claim 5 wherein the stoichometric value of the air-fuel mixture is essentially 14.5/1. 
     
     
       7. The system claimed in claim 5, wherein: the means for continuously sampling the air-fuel mixture comprises a burning chamber, the burning chamber being connected to the intake manifold adjacent the first location via a valve means for preventing ignition spreading from the burning chamber into the intake manifold and having continuous ignition means, for continuously receiving portions of the mixture flowing adjacent the first location and continuously burning the portions received, and   the means for continuously adjusting said first fuel pumping means comprising an oxygen sensor, located in the burning chamber, for continuously detecting the oxygen present in the combustion chamber and continuously generating an output signal, which varies with the amount of oxygen detected, for adjusting the first fuel pumping means.   
     
     
       8. The system claimed in claim 5 wherein the second fuel pumping means comprises a fuel pump having a fuel nozzle communicating with the intake manifold and having a normally closed fuel valve and a pressure actuated solenoid communicating with the intake manifold, responsive to a relative vacuum below a predetermined value to become energized and open the fuel valve and responsive to a relative vacuum above the predetermined value to become de-energized and close the fuel valve.